1. Technical Field
This invention relates to constant velocity stroking joints.
2. Related Art
Constant velocity (xe2x80x9cCVxe2x80x9d) joints have particular application in front wheel drive systems for automotive vehicles. Power is transmitted from the transmission to the drive wheels via shaft assemblies. The shaft assemblies include CV joints at their inboard and outboard ends. The inboard CV joint is coupled to the transmission and the outer CV joint is coupled to the drive wheels. During normal operation of a front wheel drive vehicle, the wheels move up and down, and thus provision must be made for both angular and axial movement of the shaft assembly.
In a typical front wheel drive system, the outboard CV joints are designed to accommodate large joint angularity, but no axial stroking. The inboard CV joints are designed to accommodate axial stroking and joint angularity. The present invention is concerned with the stroking type CV joints. FIGS. 1-3 illustrate a prior art CV stroking joint which is commonly referred to the industry as a xe2x80x9cball spline Rzeppa jointxe2x80x9d. The joint 11 includes a half shaft 13 splined to one end of which is an inner race 15 accommodated within an intermediate race 17 which in turn is disposed within an outer race 19. A plurality of balls 21 are carried in ball grooves between end inner race 15 and intermediate race 17 and are captured within windows of a ball cage 23 to provide angular or pivotal movement of the inner race 15 and thus the shaft 13 relative to the intermediate and outer races 17, 19, respectively. Axial or plunging movement of the joint 11 is provided between the intermediate race 17 and outer race 19.
The intermediate race 17 is formed on its outer surface with a plurality of axial ball guides 25 that correspond in number and alignment with ball guides 27 formed on the inner surface of the outer race 19. A row of spline balls 29 is disposed in each of the aligned ball guides 25, 27 to provide rolling support of the intermediate race 17 within the outer race 19. Referring to FIGS. 2-4, it will be seen that the outer surface of the intermediate race 17 is formed with a pair of retaining ring grooves 31 adjacent it opposite axial ends, and that the spline balls 29 are captured between retaining rings 32 within the grooves 31 and thus cannot move beyond the ends of the intermediate race 17.
It will be appreciated thus from FIGS. 3 and 4 that the space between the retaining rings 32 is greater than the space occupied by the spline balls 29, such that there is a certain amount of open space to accommodate free rolling movement of the spline balls as the intermediate race 17 is moved axially relative to the outer race 19. FIG. 3 shows the joint 11 with the intermediate race 17 moved to the forward limit (to the left in the drawings) of free rolling stroke of the intermediate race 17 within the outer race 19. It will be seen that the spline balls 29 are confronting the rearward retaining ring (to the right in FIG. 3) and thus are no longer free to roll in the ball guides in response to additional forward axial movement of the intermediate race 17 to the left in FIG. 3. FIG. 4 shows the opposite extreme of inward free rolling stroke of the intermediate race 17 relative to the outer race 19. It will be seen that in each case of the free rolling limit, there remains an axial gap or space 33 between end stops 35, 37 of the outer race 19, and corresponding end stops 39, 41 of the intermediate race 17 which provides for additional forward and rearward axial displacement or stroking of the intermediate race 17 within the outer race 19. In practice, the joint 11 operates in the zone of free rolling stroke until such point as the extreme free stroke limits are reached, as shown in FIGS. 3 and 4. If a sufficient axial stroking force is applied to the joint 11, additional axial displacement or stroking of the intermediate race 17 occurs to close the forward or rearward gap 33, but such requires the balls 21 to slide or skid along the ball guides 27 of the outer race 19 rather than rolling, as they are restrained against rolling by confrontation with the retaining rings of the intermediate race 17.
It is an object of the present invention to improve upon such joints by increasing the free rolling travel or displacement of the intermediate race within the outer race.
A constant velocity stroking joint constructed according to the invention includes an outer race having a plurality of axially extending ball channels. An inner race is disposed within the outer race and an intermediate race is disposed between the inner and outer races and supports the inner race for angular pivotal movement relative to the outer race. The intermediate race is formed on its outer surface with a plurality of axially extending ball channels aligned with the ball channels of the outer race. The intermediate race has opposite axial ends and abutments positioned to confront the end stops of the outer race at extreme limits of axial stroking of the intermediate race within the outer race. Axially extending rows of spline balls are disposed between the intermediate race and the outer race in registry with the aligned ball channels to provide rolling support to the intermediate race during the axial stroking within the outer race. According the invention, the rows of spline balls are supported to extend beyond the ends of the intermediate race in such manner as to provide free rolling guidance of the spline balls during the axial stroking the intermediate race between the extreme limits of axial stroking of the intermediate race within the outer race.
The invention thus has the advantage of providing free rolling support to the intermediate race during its full travel within the outer race. Such support of the spline balls eliminates or greatly minimizes any sliding or skidding movement of the spline balls as with the prior art device described above.
Eliminating the skidding of the spine balls provides for a smoother, quieter CV joint and eliminates any shutter or vibrations which may be associated with such skidding of the balls inherent in the prior art constructions.
Providing full free rolling support of the balls during the full stroke of the intermediate race has the further advantage of prolonging the operating life of the joint by decreasing wear on the spline balls and associated ball channels attributed to skidding action of the spline balls.